Ultrasonic Cleaning of Marine Geophysical Equipment

ABSTRACT

Various methods and apparatuses for facilitating cleaning of submerged geophysical equipment using sound waves transmitted at ultrasonic frequencies are disclosed. In some embodiments, one or more transducers may be configured to transmit sound at one or more ultrasonic frequencies. The sound at ultrasonic frequencies may be transmitted in the vicinity of submerged geophysical equipment, such as a sensor streamer towed behind a survey vessel. Obstructions (e.g., barnacle larvae) adhering to surfaces of the geophysical equipment may be loosened or removed altogether when ultrasonic transmissions occur within its vicinity. The transducers used to transmit the ultrasonic frequencies may be implemented in various ways, such as being attached to a remote operated vehicle, a cleaning unit, or as being an integral component of the geophysical equipment.

BACKGROUND Background Description

Marine seismic surveys utilize sound waves transmitted to the earth'scrust and reflected back to recording sensors. The recording sensors maybe hydrophones in one of a number of streamers that may be towed behinda survey boat. The survey boat may tow an array of multiple streamers inparallel. When towed behind the survey boat, the streamer may besubmerged. A sound source may also be towed in the water behind thesurvey boat for transmitting the sound waves to be received by thehydrophones of the streamers. One common application of marine seismicsurveying is oil and gas exploration in marine environments. Moreparticularly, sound waves received during a marine seismic survey may beanalyzed to locate hydrocarbon bearing geological structures, and thusdetermine where deposits of oil and natural gas may be located.

Periodically, cleaning operations may be conducted on streamers used inmarine seismic surveys. Cleaning operations may be conducted by a crewon a workboat separate from the survey boat. To clean a particular oneof the towed streamers, the workboat crew may lift the streamer out ofthe water, clean by hand, and lower the streamer back into the water.Since the streamers can have significant length, (e.g., 8 km), in somecases only a portion of the streamer is lifted out of the water. Theworkboat crew may progressively lift portions of a particular streamerout of the water until cleaning is complete. The workboat crew may thenprogress to the next streamer and repeat the process. The process may besubsequently repeated until all streamers have been cleaned. The processof cleaning using a workboat crew can be very time consuming, and insome cases, dangerous to the crew members that perform the work.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects of the disclosure will become apparent upon reading thefollowing detailed description and upon reference to the accompanyingdrawings which are now described as follows.

FIG. 1 is a diagram of one embodiment of an arrangement for conducting amarine geophysical survey using an array of towed submerged streamers.

FIG. 2 is a diagram illustrating one embodiment of a cleaning apparatusconducting a cleaning of geophysical equipment using ultrasonicfrequencies.

FIG. 3 is a diagram illustrating one embodiment of a sensor streamerhaving a plurality of sensors and a plurality of transducers integratedtherein.

FIG. 4 is a diagram of one embodiment of a chase vessel and a remotelyoperated vehicle (ROV) controlled therefrom.

FIGS. 5A and 5B are diagrams illustrating one embodiment of a ROVattaching a streamer cleaning unit (SCU) to a submerged streamer beingtowed behind a boat.

FIG. 6 is a diagram illustrating one embodiment of a SCU propellingitself along a streamer to conduct a cleaning operation.

FIG. 7 is a diagram illustrating one embodiment of an ROV retrieving anSCU from a submerged streamer towed behind a boat.

FIG. 8 is a diagram illustrating one embodiment of an ROV conducting acleaning of a submerged sensor streamer using an attached cleaningapparatus.

FIG. 9 is a flow diagram illustrating one embodiment of a method forconducting a cleaning operation of a sensor streamer using an SCUcapable of transmitting sound at ultrasonic frequencies.

FIG. 10 is a flow diagram illustrating one embodiment of a method forcleaning a sensor streamer using a cleaning apparatus controlled by anROV that includes transducers for transmitting ultrasonic frequencies.

FIG. 11 is a flow diagram illustrating one embodiment of a method forcleaning a sensor streamer having integrated transducers fortransmitting ultrasonic frequencies integrated therein.

FIG. 12 is a flow diagram illustrating one embodiment of a method forcleaning geophysical equipment using one or more transducerstransmitting ultrasonic frequencies.

While the embodiments disclosed herein are susceptible to variousmodifications and alternative forms, specific embodiments thereof areshown by way of example in the drawings and will herein be described indetail. It should be understood, however, that the drawings anddescription thereto are not intended to limit the disclosure to theparticular forms disclosed; on the contrary, the disclosure is intendedto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the present disclosure as defined by theappended claims.

DETAILED DESCRIPTION

This specification includes references to “one embodiment” or “anembodiment.” The appearances of the phrases “in one embodiment” or “inan embodiment” do not necessarily refer to the same embodiment.Particular features, structures, or characteristics may be combined inany suitable manner consistent with this disclosure.

The present disclosure is directed to method and apparatus embodimentsin which ultrasonic frequencies are used to clean submerged geophysicalequipment. The ultrasonic frequencies may be transmitted by any type oftransducer or other device capable of generating sound waves at thosefrequencies. The transmission of the ultrasonic frequencies may be usedto facilitate the cleaning of various obstructions from the geophysicalequipment. Such obstructions may include (but are not limited to)barnacle larvae, barnacles, and ice. In various embodiments, thegeophysical equipment may be a sensor streamer that may be towed behinda survey vessel, although other types of geophysical equipment may alsobe cleaned using ultrasonic frequencies. As used herein, the term“ultrasonic” refers to frequencies above the range of normal humanhearing, at least including frequencies greater than 20 kHz.

In various embodiments, a cleaning apparatus may include one or moretransducers configured to transmit sound at ultrasonic frequencies. Inone embodiment, a number of transducers may be integrated into a sensorstreamer. The transducers may be periodically activated, or activatedresponsive to a command by a user at a control input. In anotherembodiment, a cleaning apparatus may include a streamer cleaning unitthat is attachable to a sensor streamer. In addition to brushes andother mechanisms for physically removing obstructions from a sensorstreamer, the streamer cleaning unit may also include one or moretransducers that may be activated during a cleaning operation. In yetanother embodiment, a cleaning apparatus may include a remotely operatedvehicle having transducers capable of transmitting sound at ultrasonicfrequencies.

Various embodiments of a method for cleaning geophysical equipment mayinclude transmitting ultrasonic frequencies in the vicinity of thegeophysical equipment. As used herein, the terms “in the vicinity” and“in a vicinity” refers to a location sufficiently near to thegeophysical equipment that the transmission of the ultrasonicfrequencies may effectively remove or at least loosen some obstructionsthereof or other undesired matter attached thereto. Since the power atwhich the ultrasonic frequencies are transmitted may vary, the terms “inthe vicinity” and “in a vicinity” may also be variable based on thetransmission power. In one exemplary embodiment, transmissions may bemade from 20 centimeters at a transmission power of 10 watts or greaterusing directional transducers to transmit the ultrasonic frequencies ina directed manner. It is noted that this example is not intended to belimiting, and the transmission power may be varied from one embodimentto the next.

The transducers used in the cleaning operations discussed herein maytransmit sound at one or more ultrasonic frequencies. In one embodiment,the ultrasonic frequency at which sound is transmitted may be a discretefrequency which has been determined to be effective for the desiredcleaning operation. In another embodiment, sound may be transmitted atmultiple, discrete ultrasonic frequencies, sequentially or concurrently.In still another embodiment, the transmission of sound at ultrasonicfrequencies may be performed by sweeping across a range of frequencies(e.g., between 20 kHz and 100 kHz). Sweeping of frequencies may begin ata high frequency and descend to a low frequency, or may begin at a lowfrequency and increase to a high frequency.

Turning now to FIG. 1, a diagram of one embodiment of an arrangement forconducting a marine geophysical survey using an array of towed submergedstreamers is shown. In the embodiment shown, tow vessel 100 is towing anarray of submerged streamers 104. Examples of such streamers may befound in U.S. Pat. No. 7,834,632 by Tenghamn et al. and U.S. Pat. No.8,098,542 by Hillesund et al., each of which is incorporated herein byreference. Each of the submerged streamers may include a number ofseismic sensors, EM receivers, or a combination thereof. The types ofsensors that may be implemented in a given streamer include (but are notlimited to) hydrophones and geophones. The types of receivers that maybe implemented in a given streamer include (but are not limited to)electrodes and magnetometers. Moreover, a given streamer may includemore than one type of sensor (e.g., a combination of hydrophones andgeophones) or receiver (e.g., a combination of electrodes andmagnetometers). Various operational considerations may make certainstreamer towing depths advantageous. In some embodiments, single sensorstreamers 104 may be towed at depths between about 4 meters and 30meters. In some embodiments, dual sensor streamers may be towed atdepths between 15 and 30 meters.

Tow vessel 100 may also tow a number of sources 102 via tow cables 103.In some embodiments, sources 102 may be towed by another vessel (notshown). Sources 102 may include a variety of seismic sources, such asmarine vibrators or air guns. Sources 102 may also include a variety ofelectromagnetic (EM) sources, such as antennas or magnetic coils. Insome embodiments, sources 102 may transmit sound waves into the water,the echoes of which may be detected by the seismic sensors of thestreamers 104. In some embodiments, sources 102 may transmit EM signalsinto the water, which may be detected by the EM receivers of thestreamers 104. The sensors and receivers of streamers 104 may beelectrically coupled to electronic equipment aboard tow vessel 100 thatmay be used to analyze geophysical data, such as received echoes ordetected signals. Using the arrangement shown in FIG. 1, marinegeophysical surveys may be conducted. Among the uses of informationobtained from such surveys may be the identification of geologicalformations indicative of oil and/or natural gas deposits.

During the conduct of marine geophysical surveys, equipment may at timesbecome obstructed. For example, the growth of barnacles and barnaclelarvae on streamers may occur during the conduct of marine geophysicalsurveys, particularly in certain geographic locations. In coldergeographic locations, ice may sometimes form on geophysical surveyequipment such as the streamers discussed herein. When obstructions suchas barnacles are attached to the streamers, the sensitivity of thesensors and receivers contained therein may be reduced. This in turn canadversely affect the data collected in the survey. Accordingly, cleaningof the streamers may be periodically performed in order to removeobstructions from the streamers 104 and thus to increase theeffectiveness of a survey in progress.

In some embodiments, the cleaning of the streamers (and more generally,of geophysical equipment) may include transmission of sound at one ormore ultrasonic frequencies. The sound may be transmitted toward thegeophysical equipment undergoing the cleaning operations. Transmissionof sound at one or more ultrasonic frequencies may be effective inloosening or removing various obstructions that may otherwise adhere tothe geophysical equipment. Such obstructions that may be loosened orremoved using sound transmitted at one or more ultrasonic frequenciesmay include, but are not limited to, barnacle larvae, barnacles, andice. In cases where the obstructions are not completely removed,additional cleaning using brushes and/or other types of cleaningapparatuses may be utilized to complete the cleaning.

FIG. 2 is a diagram illustrating one embodiment of a cleaning apparatusconducting a cleaning of a piece of geophysical equipment usingultrasonic frequencies. In the embodiment shown, cleaning apparatus 10includes a number of transducers 20 that are configured to transmitsound at one or more ultrasonic frequencies. As used herein, the termtransducer refers to any device or apparatus capable of transmittingsound at ultrasonic frequencies. Such apparatus/device embodiments mayinclude (but are not limited to) speakers and piezoelectric transducers.The sound at one or more ultrasonic frequencies may be transmitted inthe vicinity of (and in this particular example, directly toward)geophysical equipment 25. The transmission at one or more ultrasonicfrequencies may loosen or remove obstructions (such as those mentionedabove) adhering to external surfaces of geophysical equipment 25.

FIG. 3 is a diagram illustrating one embodiment of a sensor streamerhaving a plurality of sensors and a plurality of transducers integratedtherein. In the embodiment shown, sensor streamer 104 includes a numberof sensors 111. The sensors may include acoustic sensors, magneticsensors, or any other type of sensors suitable for use in submergedstreamers such as those shown in FIG. 1.

In addition to the sensors 111, sensor streamer 104 also includes aplurality of transducers 113. The transducers 113 in the embodimentshown may be configured to transmit sound at one or more ultrasonicfrequencies. A control unit 120 coupled to sensor streamer 104 may beused to activate the transducers 113 in order to cause them to transmitsound responsive to a user input. Inputs from control unit 120 in someembodiments may determine the ultrasonic frequencies at which sound istransmitting. Sound may be transmitted at a single ultrasonic frequency,at a number of discrete ultrasonic frequencies (sequentially orconcurrently), or by sweeping across a range of ultrasonic frequencies.Sound transmitted at one or more ultrasonic frequencies by transducers113 may facilitate the cleaning of sensor streamer 104, and moreparticularly, for loosening or removing obstructions otherwise adheredthereto.

Streamer 104 in the embodiment shown also includes a streamer telemetryunit (STU) 116. STU 116 may be used to perform measurements based on rawdata received from the sensors 111, and may also transmit measurementdata to receiving equipment on tow vessel 100. STU 116 may besusceptible to attracting barnacles and barnacle larvae. Accordingly,one or more transducers 113 may be located in the vicinity of STU 116,if not within the unit itself.

Cleaning of survey equipment (e.g., streamers 104, sources 102, or towcables 103) as discussed herein may, in some embodiments, be facilitatedby the use of an ROV. Turning now to FIG. 4, a diagram of one embodimentof a chase vessel and an ROV controlled therefrom is illustrated. In theembodiment shown, chase vessel 105 is a boat separate from tow vessel100 discussed above, and may be used in the conduct of survey equipmentcleaning operations. An ROV 200 is tethered to chase vessel 105 by acable 110 in the illustrated example. Cable 110 may be used to transfersignals between ROV 200 and a control unit 115 located on chase vessel105. An operator at control unit 115 may maneuver ROV 200 using variouscontrols that generate commands sent to ROV 200 via cable 110.Similarly, various types of feedback (e.g., visual, audio, etc.) may berelayed from ROV 200 to control unit 115. Cable 110 may be of sufficientlength to allow ROV to traverse the entire length of a streamer whilethe chase vessel is at a distance and/or relatively stationary withrespect to the streamer.

In the embodiment shown, ROV 200 includes one or more transducers 211that may be configured to transmit sound at ultrasonic frequencies. Inconducting a cleaning operation, ROV 200 may be maneuvered into thevicinity of a streamer while transmitting sound from transducer(s) 211.As is discussed below, in one embodiment a cleaning method includes anROV 200 causing a cleaning attachment to traverse the length of astreamer while sound is transmitted at ultrasonic frequencies bytransducer(s) 211 as ROV 200 moves cleaning attachment to move along thestreamer.

In some embodiments, ROV 200 may be used to facilitate cleaning of astreamer by attaching an SCU thereto, wherein the SCU includestransducers configured to transmit sound at ultrasonic frequencies.FIGS. 5A and 5B are diagrams illustrating one embodiment of a ROVattaching an SCU unit to a submerged streamer being towed behind a boat.In FIG. 5A, an SCU 205 has been attached to ROV 200. The attachment ofthe ROV 200 to SCU 205 may occur either with at least one of them abovethe waterline or with both submerged in the water. Under control of anoperator at control unit 115, ROV 200, with SCU 205 attached thereto,may be maneuvered to a streamer 104 to be cleaned while the streamer issubmerged and being towed behind a tow vessel 100.

SCU 205 in the embodiment shown includes a cleaning apparatus 213. Moreparticularly, cleaning apparatus 213 may include one or more transducersfrom which sound may be transmitted at one or more ultrasonicfrequencies. These transducers may be activated once SCU 205 is attachedto the streamer 104.

In FIG. 5B, ROV 200 has been maneuvered into position near streamer 104.More particularly, ROV 200 has been maneuvered into position to attachSCU 205 to the submerged streamer 104. In this particular example, ROV200 has been maneuvered to attach SCU 205 to a forward end (e.g., theend closest to the tow vessel) of streamer 104. After SCU 205 has beenattached to streamer 104, ROV 200 may release the SCU 205 to commence acleaning operation. Since SCU 205 is attached to streamer 104 while bothare submerged, there is no need to bring streamer 104 to the surface.Upon attachment to streamer 104, the transducer(s) of cleaning apparatus213 may begin transmitting.

FIG. 6 illustrates the streamer cleaning operation using SCU 205. In theillustrated example, ROV 200 has released SCU 205 subsequent to itsattachment to streamer 104. Upon its release, the illustrated embodimentof SCU 205 is propelled from the forward end of streamer 104 to the rearend by hydrodynamic drag. As SCU 205 traverses along streamer 104,transmission of sound at one or more ultrasonic frequencies may aid thecleaning. The transmission of sound at ultrasonic frequencies may removesome obstructions (e.g., barnacle larvae) previously adhering tostreamer 104. Furthermore, other obstructions may be loosened by theultrasonic frequency transmissions. Brushes or other physical cleaningapparatuses implemented on SCU 205 may cause these loosened obstructionsto be permanently removed as SCU travels down the length of streamer104.

In the example shown in FIG. 7, SCU 205 has reached the end of streamer104. Streamer 104 includes a stopper 107 to hold SCU 205 in place whileROV 200 is maneuvered into position for retrieval. In the illustratedexample, ROV 200 has been maneuvered into place in order to re-attach toSCU 205. Upon re-attachment of SCU 205 to ROV 200, SCU 205 may beremoved from streamer 104. ROV 200 may then be maneuvered into positionto attach SCU 205 to another streamer 104, or may be maneuvered back tochase vessel 105 where it may be taken on board.

FIG. 8 illustrates another type of cleaning operation that may befacilitated by an embodiment of ROV 200. In this example, ROV 200 has acleaning tool 210 attached thereto. In one embodiment, ROV 200 may beconfigured for attachment of either SCU 205 or cleaning tool 210, bothof which may be removable subsequent to attachment. Cleaning tool 210may be arranged for a more thorough cleaning of a streamer 104 relativeto the cleaning performed using SCU 205. Furthermore, ROV 200 may remainattached to cleaning tool 210 throughout the operation of cleaning astreamer 104. To perform the cleaning operation, ROV 200 may bemaneuvered into close proximity to streamer 104 such that cleaning tool210 may be attached to the streamer. ROV 200 may then propel cleaningtool 210 along the length of streamer 104, and may make multiple passesif desired. ROV 200 may also transmit sound at one or more ultrasonicfrequencies from transducer(s) 211 during the cleaning operation. Thismay further increase the effectiveness of the cleaning by removing someobstructions while loosening others, thereby making their removal bycleaning tool 210 easier. Upon completion of the cleaning operation, ROV200 may detach cleaning tool 210 from streamer 104.

Turning now to FIG. 9, a flow diagram of one embodiment of a method forconducting a cleaning of a submerged, towed streamer using an ROV and astreamer cleaning apparatus is shown. In the embodiment shown, method700 begins with the attachment of an SCU to an ROV (block 705). Theattachment of the SCU to the ROV may be performed while both are in thewater and submerged, although it is also possible and contemplated thatan SCU may be attached to an ROV prior to submerging them in water.

With the SCU attached to the ROV, the ROV may then be maneuvered intoclose proximity to the streamer to be cleaned (block 710). In oneembodiment, the ROV may be maneuvered into a position near the end ofthe streamer closest to the tow boat. When in close enough proximity,the SCU may be attached to the streamer (block 715). The SCU may bereleased from the ROV after having been securely attached to thestreamer (block 720).

After the ROV has released the SCU, cleaning of the streamer maycommence. The SCU discussed in this embodiment is a self-propelled unit,and may traverse the length of the streamer while transmitting sound atultrasonic frequencies from one or more transducers (block 725). Afterthe SCU has reached the end of the streamer, it may be held in place bya stopper in order to prevent it from becoming unintentionallyde-attached from the streamer. The ROV may be maneuvered into positionfor re-attachment of the SCU (block 730). After re-attachment to theROV, the SCU may be removed from the streamer for retrieval or forcleaning of another streamer.

FIG. 10 is a flow diagram of one embodiment of a method for conducting acleaning of a submerged, towed streamer using an ROV and an attachedcleaning apparatus. Method 800 begins with the attachment of a cleaningtool to an ROV (block 805). After the cleaning tool is securelyattached, the ROV may be maneuvered to a streamer to be cleaned (block810). The ROV may maneuver into such a position that the cleaning toolis attached to the streamer (block 815).

Upon attaching the cleaning apparatus to the streamer, the cleaningoperation may commence. The ROV may propel the cleaning apparatus alongthe streamer, traversing its length (block 820). The ROV in oneembodiment may include one or more transducers, and may thus transmitsound at one or more ultrasonic frequencies as it propels the cleaningtool along the streamer. Upon reaching the end of the streamer (or theend of the portion to be cleaned), the ROV may detach the cleaning toolfrom the streamer (block 825). The cleaning tool may then be returned toa chase vessel for retrieval, or the ROV may be maneuvered into positionto clean another streamer.

FIG. 11 is a flow diagram of a method for conducting a cleaning in whichultrasonic frequencies are transmitted from transducers integrated intoa streamer. In method 900, a streamer is towed behind a survey vessel(block 905). The streamer may be one of a number of streamers in anarray, although embodiments are possible and contemplated wherein only asingle streamer is towed. During the conducting of a cleaning operation,the transducers integral to the streamer may be activated to transmitsound at one or more ultrasonic frequencies. Cleaning may also be aidedby other types of cleaning devices (e.g., the SCU or cleaning tooldiscussed above) in some embodiments.

Turning now to FIG. 12, a flow diagram illustrating one embodiment of amethod for cleaning geophysical equipment using one or more transducerstransmitting ultrasonic frequencies is shown. Method 950 in theembodiment shown comprises the transmission of sound at one or moreultrasonic frequencies by one or more transducers in the vicinity of thegeophysical equipment to be cleaned (block 955). As noted above, thetransmission of sound at ultrasonic frequencies may either loosen orremove altogether obstructions such as barnacle larvae that are attachedto the external surfaces of the geophysical equipment. In someembodiments, certain frequencies may be particularly effective inremoving obstructions, although transmissions may occur over a range offrequencies or at a number of different discrete frequencies.

Numerous variations and modifications will become apparent to thoseskilled in the art once the above disclosure is fully appreciated. It isintended that the following claims be interpreted to embrace all suchvariations and modifications.

What is claimed is:
 1. A method comprising: towing geophysical equipmentbehind a survey vessel; and cleaning the geophysical equipment while thegeophysical equipment is being towed, wherein said cleaning is performedat least in part by transmission of sound at an ultrasonic frequency. 2.The method as recited in claim 1, wherein the transmission of sound atthe ultrasonic frequency is performed at least in part by a plurality oftransducers internal to the geophysical equipment.
 3. The method asrecited in claim 1, wherein the transmission of sound at the ultrasonicfrequency is performed at least in part by one or more transducerscoupled to a remotely operated vehicle (ROV).
 4. The method as recitedin claim 3, wherein the geophysical equipment is a sensor streamer, andwherein the method further comprises: the ROV traversing the length ofthe sensor streamer; and transmitting sound at the ultrasonic frequencytoward the sensor streamer during said traversing the length of thesensor streamer.
 5. The method as recited in claim 1, wherein thegeophysical equipment is a sensor streamer, and wherein the transmissionof sound at the ultrasonic frequency is performed at least in part byone or more transducers coupled to a streamer-cleaning unit (SCU) thatis attachable to the sensor streamer.
 6. The method as recited in claim5, further comprising: attaching the SCU to the a first end of thesensor streamer; the SCU traversing from the first end to a second endof the sensor streamer; and the SCU transmitting sound at the ultrasonicfrequency during said traversing.
 7. The method as recited in claim 1,wherein the transmission of sound at the ultrasonic frequency furtherincludes transmitting sound at a plurality of ultrasonic frequencies,and wherein the transmitted sound is generated externally to thegeophysical equipment and directed toward the geophysical equipment. 8.The method as recited in claim 7, wherein said transmitting sound at aplurality of ultrasonic frequencies comprises sweeping across a range ofultrasonic frequencies.
 9. An apparatus comprising: a cleaning unitconfigured to clean one or more pieces of geophysical equipment,including by transmission of ultrasonic frequencies.
 10. The apparatusas recited in claim 9, wherein the one or more pieces of geophysicalequipment include a sensor streamer, and wherein the apparatus includesthe cleaning unit and the sensor streamer.
 11. The apparatus as recitedin claim 9, wherein the one or more pieces of geophysical equipment isinclude a sensor streamer, and wherein the apparatus is a streamercleaning unit (SCU) that includes one or more transducers configured totransmit sound at ultrasonic frequencies.
 12. The apparatus as recitedin claim 9, wherein the apparatus is located in a remotely operatedvehicle (ROV), and wherein the ROV includes one or more transducersconfigured to transmit sound at ultrasonic frequencies.
 13. Theapparatus as recited in claim 9 wherein the one or more pieces ofgeophysical equipment include a sensor streamer, and wherein thecleaning unit comprises one or more transducers configured to transmitsound at ultrasonic frequencies, wherein the one or more transducers areintegrated in the sensor streamer.
 14. The apparatus as recited in claim13, further comprising a control unit coupled to the sensor streamer,wherein the control unit is configured to activate the plurality oftransducers responsive to a first input and further configured todeactivate the plurality of transducers responsive to a second input.15. The apparatus as recited in claim 9, further comprising a controlunit coupled to the cleaning unit, wherein the control unit control unitis configured to cause the cleaning unit to transmit sound by sweepingacross a range of ultrasonic frequencies.
 16. A method comprising:towing geophysical equipment in water behind a survey vessel; andtransmitting sound at one or more ultrasonic frequencies in the water ina vicinity of the geophysical equipment.
 17. The method as recited inclaim 13, wherein said transmitting comprises one or more transducers ona remotely operated vehicle (ROV) transmitting sound at one or moreultrasonic frequencies.
 18. The method as recited in claim 17, whereinthe geophysical equipment includes a sensor streamer, and wherein themethod further comprises the ROV traversing from a first end of thesensor streamer to a second end of the sensor streamer whiletransmitting sound at the one or more ultrasonic frequencies.
 19. Themethod as recited in claim 16, wherein said transmitting comprises oneor more transducers on a streamer cleaning unit (SCU) transmitting soundat one or more ultrasonic frequencies.
 20. The method as recited inclaim 19, wherein the geophysical equipment includes a sensor streamer,and wherein the method further comprises: attaching the SCU to a firstend of the sensor streamer; initiating transmission of sound at one ormore ultrasonic frequencies by the one or more transducers; the SCUtraveling from the first end of the sensor streamer to a second end ofthe streamer while transmitting sound at one or more ultrasonicfrequencies.
 21. The method as recited in claim 16, further comprising aplurality of transducers internal to the geophysical equipmenttransmitting sound at one or more ultrasonic frequencies.
 22. The methodas recited in claim 16, wherein the transmitting sound includes sweepingacross a range of ultrasonic frequencies.
 23. The method as recited inclaim 16, wherein the transmitting sound includes transmitting sound ata first ultrasonic frequency and at least one additional ultrasonicfrequency.